Stock-Based Compensation - Summary of Stock-Based Compensation Grants (Detail)	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Time Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Awards Granted | shares	12,708
Weighted-Average Grant Price Per Share | $ / shares	$ 112.42
Performance Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Awards Granted | shares	39,511
Weighted-Average Grant Price Per Share | $ / shares	$ 70.42
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Awards Granted | shares	10,630
Weighted-Average Grant Price Per Share | $ / shares	$ 112.42